Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.
Catheters are commonly used in medical practice to examine and treat the heart. They may be inserted into the cardiovascular system of the patient through small punctures in the skin. They may then extend through a vein into the heart where they sense the electrical activity of the heart. In certain types of aberrant electrical activity, some catheters may be able to treat the heart by ablating certain areas of the heart. Catheters typically include a tubular structure such as a plastic tube with one or more electrodes attached to the tip of the tube.
Many catheters use conductive metal rings as electrodes. These metal rings are positioned at various intervals along the length of the tip section of the tube. These types of ring electrodes may be used for various tasks including radiopaque markers, antennas, and sensors for sensing electrical signals. Typically, the rings are secured in place using an appropriate adhesive, or by some mechanical means such as crimping or swaging. Swaging is a process of reducing the diameter of a ductile metal tube to a smaller, predetermined diameter.
The problem with mechanical attachment is that it may allow fluid to pass between the ring and the tube. Biological fluid may then enter the tube, and may be trapped under the electrode ring or within the catheter.
An adhesive may be used to seal the region between the ring and the tube. The adhesive may also be applied to the margins or edges of the ring electrode to further improve the seal between the ring electrode and the catheter tube. The use of adhesives may, however, be problematic because particles of the resin may become detached from the catheter tube during use. This is undesirable as it presents a risk to the patient. In addition, the application process of the adhesive requires precision and makes the manufacturing process of the catheter slower and more expensive.
These problems are exacerbated for catheters that are reprocessed or reused. When a catheter tube is cleaned and sterilized after it has been used, the mechanical joint between the ring electrodes and the catheter tube may be weakened and biological matter may enter the catheter tube. Weakening of the joints and resulting failure can be particularly common after multiple reprocessing cycles. It is also possible for small particles of the adhesive to become detached during reprocessing leaving small cavities in the resin. These cavities may catch biological matter when the catheter is used, and the biological matter may, in turn, be transferred to another patient because these types of small cavities may be difficult to clean.